Radiation penetrating power

Radiographic examination is either by x-rays or by gamma radiation. The former has greater penetrating power, but the latter is more portable. Few x-ray machines can penetrate beyond 300-mm (12 -in) thickness. 

The nuclear reactor also must be shielded against the emission of radioactive material to the external environment. Suitable radiation controls include both thermal and biological shielding systems. Radiation from alpha particles (a rays) and beta particles ((3 rays) has little penetrating power, but gamma rays have deep penetration properties. Neutron radiation is, however, the primary area of risk. Typically, extremely thick concrete walls are used as a neutron absorber, but lead-lined concrete and special concretes are also used. 

Second in penetrating power is (3 radiation. These fast electrons can penetrate about 1 cm into flesh before their electrostatic interactions with the electrons and nuclei of molecules bring them to a standstill. 

Radiation Relative penetrating power Shielding required... 

Distinguish a, (3, and -y radiation by their response to an electric field, penetrating power, and relative biological effectiveness (Sections 17.1 and 17.6). 

The gamma ray is a photon of electromagnetic radiation with a very short wavelength and high energy. It is emitted from an unstable atomic nucleus and has high penetrating power. 

Gamma radiation has a very high penetrating power. A small fraction of the original stream will pass through several feet of concrete or several meters of air. The specific ionization of a gamma is low compared to that of an alpha particle, but is higher than that of a beta particle. 

Gas Ionization Counters A common gas ionization counter is the Geiger-Muller counter where the electronic pulses derived from the ionization process are registered as counts. The instrument can be adjusted to detect only radiation with a desired penetrating power. 

The great advantage of Mossbauer spectroscopy for catalyst research is that it uses 7-radiation of high penetrating power such that the technique can be applied in situ. An economic advantage is that the technique is relatively inexpensive. The price is about a factor of ten less than equipment for electron microscopy or photoelectron spectroscopy. 

Which of the following lists the types of radiation in the correct order of increasing penetrating power ... 

In order to handle radioisotopes safely it is necessary, among other things, to define fairly carefully the penetrating power of the radiation emitted by any isotope. Alpha particles, having only a relatively limited number of energy levels, are absorbed by contact with other atoms. The absorbing power of a material is referred to in terms of its equivalent thickness. The thickness required can be calculated by dividing the equivalent thickness by the density of the material. 

Figure 13.3—X-ray emission spectrum produced by an anticathode (anode), measured with a spectrometer, and schematic of an X-ray tube. The line spectrum can be observed as a superposition on the continuum spectrum. It is the continuum portion of this radiation that is solicited for applications that necessitate a high X-ray penetration power, such as for radiology. For analysis, the line spectrum is preferred. Water cooling is compulsory if the X-ray tube operates at high power (1 -4 kW).

Figure 4.5 shows the relative penetrating power of the three types of radiation, and Figure 4.6 shows an interesting practical use for gamma radiation. 

Each of the types of radiation has a characteristic way of interacting with matter and transferring its energy. Alpha radiation has the least penetrating power and its effects are limited to the surface layers of a material, so it only needs to be considered when a surface is contaminated by an alpha emitter. Beta radiation has a range of up to a centimetre or two whilst X-ray, gamma... 

In addition to the penetrating power of the x-rays there are certain other characteristic phenomena encountered in radiography with the betatron not found with low voltage x-rays, such as a) A relative freedom from scattered radiation. The secondary radiation will tend to retain direction which the primary radiation originally had. Hence, no blocking is necessary around an irregular object or be-... 

The fact that there were three basic decay processes (and their names) was discovered by Rutherford. He showed that all three processes occur in a sample of decaying natural uranium (and its daughters). The emitted radiations were designated a, (3, and y to denote the penetrating power of the different radiation types. Further research has shown that in a decay, a heavy nucleus spontaneously emits a 4He nucleus (an a particle). The emitted a particles are monoenergetic, and, as a result of the decay, the parent nucleus loses two protons and two neutrons and is transformed into a new nuclide. All nuclei with Z > 83 are unstable with respect to this decay mode. 

The three principal types of nuclear radiation penetrate matter to different extents. Table 17.3 summarizes the penetration power of each type. 

The emission of nuclear particles or radiation from an isotope during its disintegration is commonly referred to as radioactivity. These emissions are classified as of the three basic types a, 0 and y. a-Particles, which are helium nuclei, have only weak penetrating power and may be stopped by 5-10 cm of air or thin metallic sheets. They are, however, highly energetic, ranging from 4 to 10 MeV. Thus they have a high ionization capacity... 

The relative penetrating powers of the three kinds of radiation are approximately in the range of 1,100, and 10,000 for the alpha, beta, and gamma rays, respectively. The penetrating power of alpha rays is less than 0.2 m (8 in.) of atmospheric air. Beta radiation can penetrate approximately 6 mm (0.25 in.) of aluminum. Gamma rays are used for level measurement because of their high penetrating power, and because they cannot be deflected. 

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